This invention relates generally to heat pumps and refrigeration systems and more particularly, it relates to an apparatus and method for controlling the operation of supplemental electric heaters so that the amount of energy consumption is minimized. The present invention includes a micro-processor with a program for achieving set-back automatically so as to reduce the temperature setting of a conditioned space during nighttime periods. The invention has particular applications in heat pumps for heating residential dwellings, small office buildings, mobile homes and the like.
In order to minimize the operation of supplemental electrical heaters and thus reduce energy consumption, the set point of the desired or referenced temperature in the conditioned space is set back or changed to a lower temperature reference point during nighttime periods. In the case of a commercial building, this is done when there are no occupants in the conditioned space such as when the building is closed for the night, i.e., 11 p.m. to 6 a.m. The reference temperature is typically set back to 55.degree. F. during this unoccupied period. A microprocessor under the control of a program is utilized to prevent the operation of the supplemental electric heaters as long as the higher reference set point temperature during the daytime can be reached within a pre-determined time interval.